Figure 3

Leptin and insulin activate large conductance K _ATP in ARC neurones A, representative cell-attached recording from an acutely dissociated ARC neurone. Leptin (10 nM), present in the electrode solution, increased the activity of a K⁺ channel, which was inhibited reversibly by bath application of 200 μM tolbutamide. Upward deflections in this and subsequent cell-attached recordings are extracellularly recorded action current activity. B, representative recording from an inside-out patch under asymmetrical K⁺ conditions and held at 0 mV obtained from an acutely dispersed ARC neurone, following cell-attached leptin-induced increase in channel activity. Note that bath application of 3 mM MgATP reversibly inhibited K⁺ channel activity. Inserts are expanded regions of traces showing channel activity in more detail. C, representative cell-attached recording from an acutely dissociated ARC neurone. Under control conditions, few channel openings are observed. Subsequent to bath application of 0.1 nM insulin, there is a marked increase in K_ATP channel activity. Corresponding diary plot of channel activity (N_f.P_o) with time displays the insulin induced increase in activity.